The purpose of this study is to identify risk factors and early signs of Alzheimer's Disease (AD) using the Baltimore Longitudinal Study of Aging (BLSA/National Institute on Aging), a 30-year prospective study of aging. Previous identification of risk factors for Alzheimer's Disease primarily derives from case-control studies where information is obtained from the case who suffers from diminished recall or from surrogate respondents. An advantage of the BLSA population is that subjects have been followed for up to 30 years prior to the development of dementia with extensive data collected at 2 year intervals. A nonconcurrent prospective design is imposed on the BLSA. Study subjects (active or inactive) will be traced to the present to ascertain whether they have developed the disease of interest (dementia/Alzheimer's Disease) since the inception date of the study (estimated number of dementia cases: >100; estimates cases AD: 80). Diagnoses will be determined by direct examination and appropriate laboratory studies. Impaired subjects who cannot return to the study site will be evaluated during home/nursing facility visits. Three controls per case will be selected to examine risk factors which have been reported in previous studies. These include history of head trauma, thyroid disease, maternal age at birth, cataracts and familial history of hematological malignancy. In addition, other possible risk factors ill be examined including smoking history, lipid profiles, glucose tolerance and environmental/social factors. Finally, data will be analyzed to identify early psychological changes in subjects who later develop AD including test scores on the Benton Visual Retention Test, WAIS Vocabulary, Concept Problem Solving and Guilford-Zimmerman Temperament Survey. The BLSA population provides a unique and rich source of prospective data for identifying risk factors and antecedents of disease. This is especially important for Alzheimer's Disease given the potential reporting biases inherent in previous studies and the insidious onset of illness.